1. Field of the Invention
The invention relates to a process of producing linear, small diameter, smooth surface thin wall tubular polymeric composite articles. Also, the invention relates to tubular medical articles and a process for their manufacture.
2. Description of the Prior Art
Conventional commercially available tubular medical articles of small diameter and thin wall dimensions such as hypodermic needles are manufactured from metals e.g. stainless steel. However, the metals interfere with certain diagnostic procedures such as X-rays, magnetic resonance imaging (MRI), sonograms, inter alia. To overcome this problem, plastic has been suggested as a material of construction. While the plastic material can overcome some of the deficiencies of the metal articles when used with the various diagnostic procedures, generally its mechanical properties do not approach the mechanical and chemical properties inherent in metals.
U.S. Pat. No. 5,603,696 issued to Williams, et al. discloses molded tubular medical articles produced from specific blends of syndiotatic and isotactic crystalline polypropylene, which are produced by a molding process. The invention is directed to articles having a wall thickness of about 2 mm or less with a high clarity requirement to achieve a see-through capacity. However, the patented medical articles do not possess the mechanical properties necessary for some medical procedure. For example, they would not have the stiffness required for use as hypodermic needles.
Therefore, there is a need for tubular medical articles of small diameter and thin wall dimensions which have substantially improved mechanical properties and which can be produced in a process, which is efficient, economical and reproducible.
The present invention provides linear small diameter, thin wall, and tubular articles having millimeter dimensions, particularly medical articles, which overcome the deficiencies of both metallic and plastic articles of the prior art. More particularly the present invention is directed to a process for making small diameter polymeric composite tubes having thin walls more efficiently with reproducible results.
The process of this invention, which involves a series of simple and economical steps yields reinforced polymeric composite tubular articles having high dimensional stability, a uniform and smooth surface, including surface slipperiness, abrasion resistance, high mechanical strength and corrosion resistance.
In its broadest aspect the process comprises the steps of:
a) Subjecting a flexible mandrel to a tensioning means for providing linearity along its longitudinal axis;
b) Applying a prepreg around the tensioned mandrel;
c) Releasing the tension on the mandrel;
d) Covering the prepreg coated mandrel with a compression sleeve to form an assembly;
e) Shrinking the compression sleeve the assembly;
f) Applying an effective pressure for consolidating the prepreg around the assembly;
g) Applying tension for maintaining the linearity of the assembly to the mandrel;
h) Curing the prepreg under tension to form a tubular composite around the mandrel;
i) Releasing the tension on the mandrel;
j) Withdrawing the mandrel from the cured prepreg tubular composite; and
k) Removing the compression sleeves to yield a linear small diameter, smooth surface, thin wall tubular composite article.
The invention includes tubular polymeric composite articles made by the above-described process and particularly the production of hypodermic needles. The tubular composite articles of this invention have excellent tensile strength, modulus, and impact resistance.
It is, therefore, a primary object of this invention is to provide a process for the production a linear, small diameter, smooth surface, thin wall composite polymeric tubular article.
It is another object of this invention to provide tubular medical articles for minimally invasive percutaneous introduction into a mammalian body, which does not interfere with diagnostic medical procedures.
It is a further object of this invention to provide tubular medical articles for introducing or removing fluids from a mammalian body.
Yet another object of this invention is to provide a process for preparing tubular small diameter composites useful as hypodermic needles.
These and other objects, features and advantages will become apparent from the following description of the preferred embodiments, accompanying drawings and claims.